The specific Chip is BCM43224 (14e4:4353).
The brcmsmac open source driver is supposed to work and was merged in to the kernel 2.6.37 (according to https://help.ubuntu.com/community/WifiDocs/Driver/bcm43xx). I guess that's why with Ubuntu 12.04 everything worked out of the box - but not in Trisquel.
